This invention pertains to an AC fault current limiting circuitry.
AC fault current limiters are required in electrical power systems to rapidly insert an impedance into a system when a fault occurs. In this manner instantaneous peak current can be limited to a maximum permissible value. To be effective the impedance has to be inserted within a few milliseconds on the order of less than five milliseconds without the assistance of natural current zero in an AC system.
One of the presently known fault current limiters consists of a high speed main switch which, on opening, generates a very high voltage arc to commutate the fault current rapidly to a resistor. A capacitor is also usually included in parallel with the switch so as to facilitate commutation and limit the rate of rise of voltage across the switch. The main switch required for a scheme of this kind would require the ability to generate very high voltage. However, switches of this kind are not believed to be commercially available at this time.